Conventionally, for example, there has been known a projector of so-called three-panel type which synthesizes light colors modulated by an electro optic device such as liquid crystal panels according to image information, and magnifies and projects a color image through a projection lens. An optical unit of this projector separates the light flux emitted from the light source into light colors of three primary colors of Red (R), Green (G) and Blue (B) by a dichroic mirror. Further, the optical unit modulates each color light by three pieces of the liquid crystal panels, which are the electro optic device, according to the image information, and synthesizes the light fluxes thus modulated by a cross dichroic prism.
Such a conventional projector comprises an optical unit which modulates the color light by using the liquid crystal panel which is relatively weak to heat. For this reason, the conventional projector comprises a cooling fan for sending an air to the vicinity of the liquid crystal panel of the optical unit and cooling the panel in order to avoid the damage due to the heat generated from the light source.
Meanwhile, merely to provide the cooling fan in the vicinity of the liquid crystal panel of the optical unit will only lead to the bulkiness of the projector due to the cooling fan. Further, since a projection lens is cylindrical, such a projection lens will cause a dead space around this projection lens, which is a space hard to utilize effectively.
Hence, as a conventional projector, for example, a constitution described in Japanese Patent Laid-Open No. 11-160793 is known. The projector disclosed in this Japanese Patent Laid-Open No. 11-160793 provides a cooling fan adjacent to a projection lens. Further, an exhaust side of the cooling fan is provided with an exhaust duct. This exhaust duct sends an exhaust air from the cooling fan to the vicinity of the liquid crystal panel of the optical unit from below and cools the panel. Further, a circulation duct for recovering the exhaust air sent to the optical unit from the exhaust duct is disposed over the optical unit. This circulation duct sends the recovered exhaust air to a suction side of the cooling fan after being cooled at a cooling heat sink. The conventional projector disclosed in the above-described Japanese Patent Laid-Open No. 11-160793 adopts such a constitution that a space around the projection lens is effectively utilized so as to be downsized and at the same time the dust from the outside is prevented from being mixed into the interior thereof by a closed structure which circulates the exhaust air sent from the cooling fan to the optical unit.
However, since the conventional projector disclosed in the above-described Japanese Patent Laid-Open No. 11-160793 is of a closed structure, which circulates the exhaust air from the cooling fan, there is a problem in that the structure of the projector is complicated and further downsizing thereof is hard to attempt. Moreover, since the optical unit is cooled by one cooling fan, there is also a problem in that some level of the airflow is necessary to be sent to the optical unit, thereby increasing a load of the cooling fun and making it hard to attempt the reduction in the noise.